Pyroelectricity in crystals is produced due to a change in the surface charge exhibited as a change of spontaneous polarization of crystals in response to a temperature change. The temperature dependence of the polarization change is usually weak (<1% K−1), apart from in the vicinity of a ferro- to paraelectric phase transition. In polycrystals, misalignment of crystallographic axes and elastic interaction between the grains significantly reduces the polarization, thereby reducing the pyroelectric properties of polycrystals. In particular, in nanocrystalline barium titanate (BaTiO3), the transition to the ferroelectric (pyroelectric) phase is usually partially or completely suppressed, further reducing any measurable pyroelectric properties.